DEVELOPMENT OF HYDROLOGIC HAZARD CURVES FOR ASSESSING HYDROLOGIC RISKS FOR STRATHCONA, LADORE FALLS AND JOHN HART DAMS ON THE CAMPBELL RIVER, BC

摘要

A stochastic flood model was developed for Strathcona, Ladore, and John Hart Dams on the Campbell River for use in developing flood-frequency estimates for extreme floods. The stochastic flood model utilized a deterministic flood computation model (UBC Watershed Model) and treated the hydrometeorological input parameters as variables instead of fixed values. Monte Carlo sampling procedures were used to allow the climatic and storm related input parameters to vary in accordance with that observed in nature. Hydrometeorological inputs that were treated as variables included: seasonality of storm occurrence; magnitude of extreme storm, temporal and spatial distribution of storms; temporal temperature pattern during the storm; sea-level and freezing level temperatures; hydrologic model antecedent conditions, and initial reservoir storage.The flood-frequency relationships generated by the flood model were used to estimate the Annual Exceedance Probability (AEP) of selected flood characteristics. The AEP for flood waters reaching the top of the lock blocks on Strathcona Dam (226.30 m) was estimated to be 1:5,500,000 and the annual probability of flood waters reaching the top of the impervious core (224.60 m) was estimated to be 1:34,000. The annual probability of overtopping at Ladore Dam (179.35 m) was estimated to be 1:960,000. The annual probability of overtopping of John Hart Dam (141.73m) was estimated to be 1:1,400,000 and overtopping of the impervious core, slurry wall and sheet piles (140.50m) was estimated to be 1:65,000.These flood magnitude-frequency curves are a valuable tool that bring the metric of a flood's probability, including the PMF, into the decision making process in regards to dam safety conditions. Given the speed at which computer model simulations can now be conducted, there are methods of analysis that can be efficiently implemented to refine the estimated AEP associated with extreme floods. The SEFM method is one such method that can provide dam owners with useful information to aid in dam safety decision making.